Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$200.45	9.730%	$219.9538	$219.95	$219.95	$220.00
Purchase #2	$160.76	4.821%	$168.5102	$168.51	$168.50	$168.50
Purchase #3	$35.77	7.617%	$38.4946	$38.49	$38.50	$38.50
Purchase #4	$56.49	5.479%	$59.5851	$59.59	$59.60	$59.60
Purchase #5	$229.90	11.174%	$255.589	$255.59	$255.60	$255.60
Purchase #6	$96.40	11.121%	$107.1206	$107.12	$107.10	$107.10
Purchase #7	$220.57	4.523%	$230.5464	$230.55	$230.55	$230.50
7 purchase totals =	$1,000.34		$1,079.7997	$1,079.80	$1,079.80	$1,079.80